Intersubband Quantum Cascade Infrared Laser Development

Quantum well intersubband transition devices have generated a large amount of interest over the past several years. With the demonstration of the first intersubband laser this past year at AT&T Bell Labs, a new class of laser material was introduced. The extension of this work to the GaAs/AlGaAs material system will expand the possibilities for bandgap engineering for these novel structures. The new devices, unlike traditional lasers, are unipolar. Like their detector counterpart, the Quantum Well Intersubband Photodector (QWIP), the new design freedom found in the intersubband transitions will allow emission wavelengths from 4 microns to 100 microns as well as integration of multi-wavelength emitters within the same device. The development of intersubband lasers will extend the mature technology of the GaAs/AlGaAs materials system into the 4-5 micron wavelength operating region. Current solid state laser sources operating in this region are based on lead salts which are notoriously unreliable and low powered.